Field of the Invention
The present invention relates to a photo-curable, especially ultraviolet-light-curable fluoropolyether-based rubber composition, a curing method thereof and a cured product obtained by the curing method.
Background of the Prior Art
Heat-curable fluoropolyether-based rubber compositions have excellent properties in terms of heat resistance, low-temperature performance, chemical resistance, solvent resistance and oil resistance. For this reason, heat-curable fluoropolyether-based rubber compositions are used in a wide variety of applications, typically in the automotive industry (Patent documents 1, 2, and 3). However, heat is necessary for this type of compositions to cure themselves, there arise problems such as: a relatively large space for a heating oven is required; it is difficult to apply the compositions to heat-sensitive parts or to large-size parts which are too large to place in a heating oven; and productivity decreases because a casting process of the composition requires batch type.
In contrast, room temperature (RT) curable fluoropolyether-based rubber compositions have been invented such as compositions of condensation cure type or amide-crosslinked type. These compositions not only dispense with heat in forming cured products but also the cured products have good properties including heat resistance, low-temperature performance, chemical resistance, solvent resistance and oil resistance as disclosed in Patent documents 4 to 8. These compositions are expected to have a variety of applications. However, such RT curable fluoropolyether-based rubber compositions have problems of balancing storage stability and fast curability, such as a problem of increased viscosity with the lapse of time during storage or a problem of taking 24 hours or more for the composition to cure themselves.
Also, in the field of silicone elastomer material, patent documents 9 and 10 disclose photo-curable compositions having good storage stability without any exposure of light and superior curability when exposed to light by using a photoactive hydrosilylation catalyst which activates a catalyst through an irradiation of UV light in the range from 230 to 400 nm. However, the photo-curable compositions have problems of having insufficient chemical resistance, solvent resistance and oil resistance depending on the usage thereof.